1. Field of the Invention
The present invention relates to a cooling system for an internal combustion engine that efficiently cools an internal engine while also making an effective use of space.
2. Description of the Related Art
As a method for cooling a combustion engine, it is known to provide a ventilation path for guiding traveling air to an internal combustion engine. For example, Japanese Patent Examined Publication No. Sho. 62-56032 (paragraphs 2–3, FIG. 1) discloses such a method.
FIG. 7 is a side elevation of essential parts of a conventional vehicle. FIG. 7 shows a V-type air-cooled engine 104 having a cylinder 102 and a cylinder 103 arranged longitudinally fitted to a lower part of a main frame 101, a fuel tank 105 having a substantially U-shaped cross section so as to straddle to the left and right of the mainframe 101 fitted to an upper part of the main frame 101, and a ventilation path 106 formed between an inner surface of this fuel tank 105 and the main frame 101. It is easy to lead air to the inside of the ventilation path 106 by passing a cooling air plate 107 over the front cylinder 102 and the main frame 101 and wind inside the ventilation path 106 is guided to the rear cylinder 103 by providing a cooling air member 108 to the rear of the ventilation path 106.
In FIG. 7, air guided to the inside of the ventilation path 106 is curved downwards at almost a right angle by the cooling air member 108, which means that flow rate is lowered by resistance. Therefore, it is not possible to obtain a sufficient air volume to cool the cylinder 103. Also, if a gap between the main frame 101 and the inner surface of the fuel tank 105 is widened in order to obtain sufficient air volume, the main frame 101 will become narrower, the capacity of the fuel tanks 105 will be reduced, and space for components around the ventilation path 106 will be restricted.
A structure for directing wind to spark plugs of an internal combustion engine is also known. For example, Japanese Patent Laid-open No. Sho. 56-111215 (Paragraph 2–3, FIG. 2) discloses such a structure.
FIG. 8 is a side elevation of a cylinder head for describing a conventional cooler for an internal combustion engine. A spark plug 113 is fitted into an indentation 112 of a cylinder head 111, a head cover 114 is fitted to the cylinder head 111, and a cooling air funnel 115 for leading wind to the indentation 112 is provided on a plug cap 116 so as to be positioned further down by the head cover 114.
In FIG. 8 also, since air is curved downwards from the horizontal direction by the cooling air funnel 115 and guided to the inside of the indentation 112, and further, flows out upwards from the inside of the indentation 112, there is a large resistance to the traveling wind which lowers the flow rate of the air and it is not possible to obtain a sufficient air volume to cool the spark plug 13.
Also, since the cooling air funnel 115 is arranged so both of two spark plugs 113, 113, which are provided apart from each other, are cooled, air is also guided to a section between the two spark plugs 113, 113. Thus, it would be desirable to lead the air in this section to the higher temperature spark plugs 113, 113 in a localized manner, which would cooling efficiency.
It is an object of the present invention to improve a cooler for an internal combustion engine in order to (1) obtain sufficient air volume to cool an internal combustion engine, (2) lead cooling air in a localized manner, and (3) increase freedom of design for components arranged around the cooling air path.